This project has integrated several disciplines in an attempt to understand the pathogenesis and improve the control of Epstein-Barr virus (EBV)-associated tumors. Studies of EBV serology in the diagnosis and monitoring of patients with nasopharyngeal carcinoma (NPC), Burkitt's lymphoma (BL), and other EBV-related diseases as well as other laboratory-oriented studies were completed in this fiscal year. A factor inhibiting the stimulation of lymphocytes by EBV was found in the serum of North American, German and Malaysian patients with NPC and correlated very closely with the activity of disease. EBV-related antibodies proved to be very useful in the diagnosis and monitoring of NPC in North American and European patients.